The present invention relates to a hydraulic clamping device for axially clamping pieces of radial symmetry, such as workplaces, working tools etc., whereby the clamping device has a receiving mandrel and a base body to be slipped onto the mandrel in which base body an annular piston is floatingly arranged. The piston is displaceable by a closed hydraulic system relative to the base body against the piece to be clamped to thereby fixedly clamp that piece with a pressure element. The pressure element is provided with wedge surfaces that are symmetrical to the longitudinal axis of the clamping device which pressure element is axially displaceable with radially movable adjusting screws in order to be moved into the desired clamping position.
A clamping device of this kind is known from German Offenlegungsschrift 39 41 765 and is provided with a pressure element in the form of a conical pressure ring with s wedge-shaped radial cross-section for adjusting a piece to be clamped, for example, a hob, or any other tool of radial symmetry, respectively, a rotating workplace. The pressure element surrounds with relatively great radial play the axial extension of the annular piston and is centered by a rubber ring. In the axial direction the conical pressure ring is arranged between an adjustable threaded ring seated on the base body of the hydraulic clamping device and a spring-elastic radial flange which is threaded with a sleeve onto the mandrel so that the wedge surfaces of the pressure ring rest at corresponding slanted counter surfaces of the spring-elastic flange. Radial pressure screws of the conical pressure ring allow for a desired radial adjustment and thus a desired effect on the axial clamping forces so that the system, comprised of the receiving mandrel, hydraulic clamping device, and the piece to be clamped onto the mandrel, i.e., a tool of radial symmetry, such as a hob, a workpiece, etc. can be aligned in a desired manner, i.e., adjusted such that it is prevented that the workpiece or tool rotates out of true.
The known hydraulic clamping device after adjustment also allows for the relief of the hydraulically loaded annular piston since the plate flange is fixed in its adjusted position by the conical pressure ring and the threaded ring.
However, the known clamping device is disadvantageous because it is technically complicated and requires a relatively great constructive length especially due to the threaded ring and the conical pressure ring together with the centering rubber ring.
It is therefore an object of the present invention to provide a hydraulic clamping device of the aforementioned kind that with a simple construction provides for an optimal short axial constructive length, that is easy to operate, and especially allows for a precise adjustment with respect to trueness of revolution during positioning of the piece to be clamped.